I spent the weekend trying to diagnose a no start issue with no luck. Here’s a short description of the condition and what I’ve already checked. Any help is appreciated.
Drove the car to Carlisle two weeks ago, 180+ miles round trip with no issues. Tried to start a week later and the engine cranks but won’t catch and doesn’t sound like it tries to catch.
1975 2.0 D-Jet with 74 Case/Heads/Exhaust and 75 ECU/MPS
4k miles on engine rebuild and car has always started up easily and idled well
Stock Cam
8.0 EU Pistons
123 Ignition Distributor - Installed last year
Bosch Blue Coil - Installed last year
FJ67 Fuel Injectors - Installed with rebuild
I always try to look at the last parts I touched which were:
Replaced hose between expansion fuel tank and filler neck
Added heater hoses between electric fan and J pipes
(both done after trip and before no start)
These don’t seem related but I assumed I bumped a connection loose somewhere when installing the hose to the J pipes but I couldn’t find anything.
Checked fuel pressure at front side of the rail of cylinders 1&2 which was 28 psi when key in on position and while cranking. It slowly drops over 20mins or so. Pulled injectors from 1&2 and cranked with injectors in bottles. I confirmed fuel spray, although it didn't seem consistent.
Connected a timing light to coil, battery and #1 spark plug wire and the light would not flash when cranked. Pulled cylinder 4 spark plug wire and saw weak yellow spark with spare plug attached to wire and threads held against ground.
Checked #7 pin on 12 pin connection on relay board and measured 12V to ground with key in on position. Checked positive side of coil to ground with key in on position and measured 12V to ground.
Pulled distributor cap and everything looks new and normal.
Replaced Bosch Blue coil with older coil (which worked when removed) and no change in starting.
This also gave me an excuse to replace my 10+ year old battery so I have a new charged battery and no change to the no start situation.
This week I will pull the plugs and see if they are fouled. I might try replacing the 123 distributor with the old stock one. I also have a spare 052 ECU I can try. I'm sure this is something stupid I missed.
Edited: fixed typo for clarity
You know the drill…air…fuel….spark. Seems like you have the first two. The no flash on the timing light and weak spark leads me to suspect the coil and, secondarily the dizzy. I’d swap the coil first.
Remember that shielded plug wires can make some timing light pickups send no or weak signal.
I am assuming you have bypassed or eliminated seat belt interlock module under the passenger seat? My 74 had one and it wouldn’t start until I bypassed it.
Wiring to distributor got knocked off putting on heater tubes….because you touched it last
All great suggestions, thanks everyone. It does feel like something must have been knocked off. I’ll spend some more time on it tonight and give an update.
Seat belt interlock is bypassed with Yellow & Yellow/Red wires under seat jumped.
Started checking all connections and found this on the MPS. Will confirm it's the root cause. Looks like it's time for Jeff's FI Wiring Harness.
I could be wrong, but that doesn’t look fresh.
A burned connection like that could mean that the MPS has shorted internally. You should verify the resistances for the primary and secondary coils are in spec, and that the MPS holds vacuum.
I hadn't considered progressive fraying. It certainly is strange to have just that one wire broken. I'd be interested to know about any causal factors you discover.
Congratulations on the fix though!
That external mark looks like from a soldering iron.
Although not visible on the side of the wire that’s exposed soldering electrical connectors on engines isn’t always a good idea. The solder creeps up the wire and makes it very stiff; fatigue over time or mishandling can cause a break.
Hooray! Hope you can make the NE Gathering again.
I think if your wires break that easily, it might be time for a new harness.
What do they cost now?
More than a long flatbed ride?
The wiring harness from Bowlsby is not cheap, but the piece of mind is well worth it in the long run.
Try to fix 1st if not there are options.
.......just more expensive.
After some thought, I ordered a new Wire Harness from Jeff Bowlsby. He's a great asset to our community and I appreciate his work which allows me (a novice) to keep my car on the road. I'll post pictures of the replacement.
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